September weather forecastLewistown, MT
September
Weather in September
September is a portal from summer to fall, with a noticeable dip in temperatures from August, manifesting the onset of autumn. A highlight is that snow makes a comeback with the city receiving 1.3" (33mm), the first in four months. A decrease in sunshine hours along with an increase in cloudy days indicate shorter, cooler days ahead. The wind experiences a subtle escalation, whispering of the impending shift change. A further increase in humidity heightens September's cooling process.Temperature
In Lewistown, the average high-temperature in September decreases from a moderately hot 78.1°F (25.6°C) in August to a refreshing 67.5°F (19.7°C). Throughout the month of September, Lewistown witnesses an average temperature of 47.1°F (8.4°C).Humidity
In Lewistown, the average relative humidity in September is 52%.Rainfall
In Lewistown, Montana, in September, it is raining for 8.7 days, with typically 1.02" (26mm) of accumulated precipitation. In Lewistown, during the entire year, the rain falls for 126.2 days and collects up to 17.83" (453mm) of precipitation.Snowfall
Months with snowfall are January through June, September through December. September is the first month it typically snows. Throughout September, in the average 1 snowfall days, it receives 1.3" (33mm) of snow. In Lewistown, during the entire year, snow falls for 83.4 days and aggregates up to 45.51" (1156mm) of snow.Daylight
In Lewistown, the average length of the day in September is 12h and 32min.On the first day of the month, sunrise is at 6:38 am and sunset at 7:56 pm. On the last day of September, sunrise is at 7:16 am and sunset at 6:58 pm MDT.
Sunshine
The average sunshine in September is 10h.UV index
The average daily maximum UV index in September is 4. A UV Index value of 3 to 5 symbolizes a moderate threat to health from unprotected exposure to Sun's UV rays for the ordinary person.Note: The UV index of 4 in September translates into these instructions:
Undertake protective steps - Preventing sun damage is advised. Exposing oneself to the midday Sun can be harmful due to the strong UV radiation; limit your time outside. Tightly woven clothing, when worn loosely, shields effectively against the Sun. Observe! Snow reflection can nearly intensify the Sun's UV radiation twofold.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
Average temperature in September
Lewistown, MT
- Average high temperature in September: 67.5°F
The warmest month (with the highest average high temperature) is July (78.8°F).
The months with the lowest average high temperature are February and December (29.1°F).
- Average low temperature in September: 47.1°F
The month with the highest average low temperature is August (54.5°F).
The coldest month (with the lowest average low temperature) is February (15.3°F).
Average pressure in September
Lewistown, MT
- Average pressure in September: 29.94"Hg
The month with the highest atmospheric pressure is January (30.13"Hg).
The month with the lowest atmospheric pressure is June (29.85"Hg).
Average wind speed in September
Lewistown, MT
- Average wind speed in September: 8.5mph
The windiest months (with the highest average wind speed) are January, April and October (9.9mph).
The calmest month (with the lowest average wind speed) is August (7.4mph).
Average humidity in September
Lewistown, MT
- Average humidity in September: 52%
The month with the highest relative humidity is February (79%).
The month with the lowest relative humidity is August (47%).
Average rainfall in September
Lewistown, MT
- Average rainfall in September: 1.02"
The wettest month (with the highest rainfall) is May (3.39").
The driest month (with the least rainfall) is December (0.71").
Average rainfall days in September
Lewistown, MT
- Average rainfall days in September: 8.7 days
The month with the highest number of rainy days is May (19.3 days).
The month with the least rainy days is January (5.4 days).
Average snowfall in September
Lewistown, MT
- Average snowfall in September: 1.3"
The month with the highest snowfall is April (9.13").
The months with the least snowfall are July and August (0").
Average snowfall days in September
Lewistown, MT
- Average snowfall days in September: 1 days
The month with the highest number of snowfall days is February (15.2 days).
The months with the least snowfall days are July and August (0 days).
Average daylight in September /
Average sunshine in September
Lewistown, MT
- Average daylight in September: 12h and 30min
The month with the longest days is June (Average daylight: 15h and 48min).
The month with the shortest days is December (Average daylight: 8h and 36min).
- Average sunshine in September: 10h and 0min
The month with the most sunshine is July (Average sunshine: 11h and 48min).
The month with the least sunshine is February (Average sunshine: 5h and 30min).
Average sunshine days in September
Lewistown, MT
- Average sunshine days in September: 19.3 days
The month with the most sunshine days is September (19.3 days).
The month with the least sunshine days is April (8.3 days).
Average UV index in September
Lewistown, MT
- Average UV index in September: 4
The month with the highest UV index is July (UV index 6).
The months with the lowest UV index are January, February, March, April, October, November and December (UV index 2).
Average cloud cover in September
Lewistown, MT
- Average cloud cover in September: 23
The month with the most cloud cover is February (Cloud cover 45).
The month with the least cloud cover is July (Cloud cover 16).
Average visibility in September
Lewistown, MT
- Average visibility in September: 6mi
The months with the highest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).
The months with the lowest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).
